Four indication block signalling systems for railroads



March 20, 1.956 T. w. TlzzARD, JR., ETAL 2,739,230

FOUR INDICATION BLOCK SIGNALLING SYSTEMS FOR RAILRODS 6 Sheets-Sheet l Filed NOV. l. 1950 Bnventors T.W.TZZARD, Jr. AND LASEBECZEM THER Cttomeg March 20, 1955 T. w. TlzzARD, JR., ET AL 2,739,230

FOUR INDICATION BLOCK SIGNALLING SYSTEMS FOR RAILROADS 6 Sheets-Sheet 2 Filed NOV. ll 1950 nventorn 'TW.TIZZARDl dr. AND LA. EBEC'LEK.

THEIR (Ittorneg March 20, 1956 T. w. TlzzARD, JR., ET AL 2,739,230

FOUR INDICATION BLOCK SIGNALLING SYSTEMS FOR RAILROADS 6 Sheets-Sheet 3 Filed Nov. l, 1950 t l'snventors T.W.TIZZARD,vJY2 AND LA EBECZEK THE I R Gttorneg MalCh 20, 1955 T. w. TlzzARD, JR., ET A1. 2,739,230

FOUR INDICATION BLOCK SIGNAL-LING SYSTEMS FOR RAILROADS 6 Sheets-Sheet 4 Filed Nov. l. 1950 JMC.-

nnentors T.W.`\`1ZZARD, dr. AND L.A.5EBECZEK.

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TH EIR Gttorneg March 20, 1956 T. w. TlzzARD, JR., ET AL 2,739,230

FOUR INDICATION BLOCK SIGNALLING SYSTEMS FOR RAILROADS Filed Nov. l. 1950 6 Sheets-Sheet 5 TH EIR (Ittorneg March 20, 1956 T. w. TlzzARD, JR., ET A1. 2,739,230

FOUR INDICATION BLOCK SIGNALLING SYSTEMS FOR RAILROADS Filed Nov. l, 1950 TOWER "B" 6 Sheets-Sheet 6 xeNA 15 15DPP Bmnentors T.WTlZZARD,1Jr. AND LA. SEBECZEK E MMM THEIR (Ittomeg United States Patent FOUR INDCATION BLOCK lSIGNAL'LING SYSTEMS FR RLRADS Thomas W. Tizzard, Jr., Downers Grove, and Louis A. Sebeczek, Aurora, lll., assignors to General Railway Signal Company, Rochester, N. Y.

Application Vl\Iovember l, 19.50, SerialNo. 1921,338

S Claims. (Cl. 246-3) Trhis invention relates to railway signalling systems, and more particularly pertains to a block signalling ,svstem adapted to govern traiiic in both directions over .a stretch of single track.

lt often happens that two spaced interlocking .areas ,are connected by a stretch of single track overv which it is Aexpedient to have trac pass in opposite directions at .different times. The trahie over such a stretch Vmay be jointly governed by the operators at the two interlocking areas, or Amay be governed by a single operator atsome centralpoint. ln any event, the system must be organized to govern tbe signals in such a manner that traffic `can enter only at one end of the stretch at any one time. Also, when ysuch a `single track stretch extends for ;a.-cen .siderable distance, it is often desirable to rprovide :intermediate signals ato allow for following train movements..

number of line wires.

Generally speaking, it is proposed that the system of the present invention provide two line wires between yeach signal location which may be used for clearing signals in either direction and at the same time provide suicient control conditions thereover to elect the desired fourindication block signalling. The four control conditions on the line are positive or negative steady energization, positive and negative pulses alternately, andthe deenergization of the line. Also, apparatus is associated with the ends of ,the line wires at each signal location ,in such a manner that each pair ofline wires can be used .to transmit the control conditions in either direction. In the present embodiment, a regular three indication signal mechanism is proposed to be employed giving the usual green, yellow and red indications, which mechanism is caused'to give .a .fourth indication by hashing the yellow indication.

Another `feature .of the present invention is to provide .a system Organization which remains in .the condition lfor the direction of traic last established, but `which .can be controlled at either end by the operator to establish .traflc conditions for train movements entering the Single track stretch from .that end. l-lowever, if the signalling dor the .single track stretch is controlled by the operatorsat the opposite Aends o f .the ,stretch their joint cooperation .iS required either over a telephone or telegraph system, .or by .a separate traiic locking circuit. On -the .other hand, if the signallingsystem is controlled bya .single'qperator at a central point, then v,suitable means is providedeither .at .the central control oice or in the field to assure that signalling in both directions by the use of a minimum 'ice the .operator will endeavor to establish trac in one direction only at any particular time.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description o f the invention progresses.

ln describing the invention in detail, reference will vbe made to the accompanying drawings, in which like letter reference characters have been provided to designate simi'- 'lar parts throughout the several views with these letter reference characters being given distinctive preceding numerals characteristic of the signal locations with which such parts .are associated, and in which:

Fig. `1 illustrates by suitable symbols the track layout and signal arrangement contemplated as having the present invention applied thereto;

Fig. 2 is arepresentation of the signal indcationsgiven .during the ,presence of a train in the stretch 0f single track, and f .Figa 3A, 3B, 3C, 3D, and 3E, `when placed end v.to end, illustrate diagrammatically one form .of signalling vsystem embodying the present invention.

For the purpose .of :simplifying ythe illustration and explanation, the various parts and circuits constituting the .embodimentof the invention have been shown diagrammat-ically ,and certain conventional illustrations .have been employed, .the drawings having been Amade more with ithe Vpurpose inmind .of making it easy to understand the prinr ciples .and .modeot' operation, than with the idea of illus? .timing .thespeciic construction and arrangement of parts .that would be employed in practice. Thus, the relays .and .contacts .are illustrated in a conventional .manner and symbolsare used to indicate the connections to the termigna'ls of batteries, or other sources of electric current, instead .of showing all of the wiring connections to these terminals. The symbols and (-F) are .employed to :indicate the positive and Ynegative terminals `respectively of suitable batteries, or other sources `of direct current. In the drawings, equipment is located at Iseveral .different ,points along the trackway, and it is assumed that .suitable connecs o f direct current, as represented by the symbols, are vprovided at each of these different spaced points: as required..

.Referri-ng to lFig. l, it will be seen that la stretch of j `single track extends between an interlocking area adjacent lTower A and another interlocking area adjacent Tower B. `Signals .6, 8, 10, l2 and 14 are -provided for vgoverning tralic in an east bound direction, while-signals 7, 9, T1, 13 .and 1-5 are provided for governing trahie in a v.west bound direction. Each of these signals isassumed to be of the search'light type such as shown, for example, in the prior patent to O. S. Field, Pat. No. 1,835,150, dated December tl, 1931. Each such signal, vsuch as signal -6 Aof Fig. 3A, has an operating mechanism including an electro-magnet M for moving a spectacle SP from its normal biased position where a red indication is displayed to either of two other positions in which yellow and green indications are respectively given. A lamp 'L ,supplies the Vlight for the 'light projecting organization of the signal. 'The mechanism also includes contacts which are operated to diiferent positions depending upon the indications given 'by the signal. For example, contacts 98 and 99 assume their solid line positions while the signal indicates stop; contact 9S kmoves to the right when the signal indicates yellow; and contact 99 vmoves to the left when the .signal indicates green. However, it is to be understood that other types of signals might well be employed.

These signals, regardless of their .type are commonly constructed to give three indications such as red, yellow and green;` but, in order to provide for closer spacingtof trafc when the trame is dense, it is desirable torhavea causes the signal 6 to indicate green.

Si fourth indication which in accordance with the present invention is given by ashing the yellow indication of the regular three indication signal mechanism. This has been indicated on the drawings by a suitable legend in Fig. l as follows: Signals Give Fourth Indication by Flashing Yellow. The fourth indication is not represented in the signal symbols to avoid the erroneous impression that each signal is mechanically constructed to give four indications. This diagram of Fig. l also indicates by legend that two line wires are provided between each pair of signal locations and that these line wires are controlled by the track circuits of the respective track section.

All of the signals are normally dark except the entering signals 6 and 1S, as well as the leaving signals 7 and 14. All intermediate signals are illuminated upon the approach of a train. Since the condition of the system for the last direction of traffic remains until the traffic direction is reversed, the system may assume any one ot several different normal conditions. As shown, the last direction of traflic is assumed to have been from west to east so that the signals 10 and 12 are controlled to the yellow indicating positions and the signal S is controlled to its green indicating position. The signals 9, 11, and 13 are of course controlled to their stop or red indicating positions. The positions of the signals have been indicated by solid line signal arms; and those signal arms; and those signals which are illuminated, have such solid lines made heavy.

In Fig. 2 the operated conditions of the various signals are illustrated for a train X in the track section 1ST which is being followed by a train Y that has not entered the single track stretch. Althoughthe signals to the rear of the train are not shown as being illuminated, the indications which would be given by these signals upon the approach of the train Y have been indicated by suitable letters such as R, Y, FY, and G for red, yellow, flashing yellow, and green respectively. The line wires leading from signal 14 have positive and negative energy applied thereto alternately, but this energy is not repeated at the signal 12 because the track relay associated with the track section 15T opens the line circuit, which deenergized condition of the line circuit for signal 12 is indicated by (0). The line wires extending to signal 10 have steady negative energy supplied thereto as indicated by The .line wires leading to signal S have positive energy applied to them as indicated by (-l-). The line wires extending to signal 6 are supplied with positive and negaexample, in the Willing et al., Pat. No. 2,502,811 dated April 4, 1950. Each pair of these relays HR and DR is so connected in the line circuit for their respective signal that one relay responds only when the line circuit is supplied With energy of one polarity and the other relay responds only when the line circuit is supplied with energy of the opposite polarity.

A slow releasing relay HD is associated with each pair of line relays HR and DR, and is controlled by them so as to be energized when either of these relays is picked up providing the HD relay for the opposing signal is deenergized. Each relay HD is sutliciently slow acting as to remain picked up when its energization is dependent upon the alternate picking up of the associated relays HR and DR.

Two slow acting relays DP and DPP are associated with each pair of line relays HR and DR, and are controlled by such line relays to distinctively respond to alternate energization of the line circuit with opposite polarities. Each signal also has a green-yellow repeater relay GYP connected in the usual way to be energized when that signal is indicating green or yellow.

A ashing relay FL is associated with each signal to operate at a suitable rate under proper conditions. This flashing relay FL serves the purpose of controlling the lamp ofthe associated signal to give a flashing yellow indication under the proper tralc conditions, and also serves to control the line circuit for the section to the rear to cause it to be energized with opposite polarities alternately in a manner later to be described. Each flashing relay FL may be of any suitable type, or may be a code oscillator, but for convenience in the present disclosure, itis assumed that this relay is of the self-interrupting type, such as shown, for example, in the prior patent to O. S. Field, Pat. No. 2,097,786 dated November 2, 1937. Since such a flashing relay FL does not ordinarily have a sufcient number of contacts, a repeater relay FLP is associated with each signal tocontrol the line circuit to the ICal'.

Because the system organization is of the so-called tumble-down type, it is necessary that each intermediate signal be provided with a directional stick relay S, such as relay 8S, for example, in Fig. 3B. These directional stick relays are for the purpose of controlling the line tive energy alternately as indicated by which The signals 7, 9, 11, 13 and 1S are all in their biased stop positions and would give a red indication if illuminated as indicated by R adjacent each of the symbols. y

Referrng to Figs. 3A3E, it will be seen that the tower A is shown in Fig. 3A as governing a signal control relay 6RD while the tower B of Fig. 3E is shown as governing a signal control relay SLD. The relay GRD is for controlling traftic to the right and effecting the clearing of Isignal 6, while the relay 15LD is for controlling traffic to `the left and clearing the signal l5. it is contemplated that these relays are independently controlled from their respective towers by suitable manually operable levers in yany conventional manner. `However, it is to be understood that this control might be provided over any suitable type of communication system, either of the direct line wire type or of the code type. it is also contemplated that the present invention might well be applied to stretches of single track between passing sidings and that these relays represented as being controlled from separate towers might both be controlled by the same operator over a suitable centralized traiiic controlling system to establish the desired direction of tratiic.

Referring to Figs. 3A-3E, it will be noted that each signal has associated therewith polarized line relays HR yand DR which are so constructed as to respond to only a particular polarity. Although any suitable polarized relay may be employed, one such a relay is shown, for

circuits to the rear of their respective signals upon the passage of a train.

All of the line circuits are controlled by the respective track relays of the associated track sections. In addition, an approach relay A is located at each signal and is included in the line circuit connection when energy vis supplied to it at that signal location. An approach repeating relay AP serves to bridge any transient deenergizations of the associated approach relay A, as later discussed. By the use of such approach relays associated with the line circuits which are track circuit controlled, it is possible to approach light the intermediate signals.

It is believed that the various other features of the present invention as well as the underlying principles thereof may be best understood by further description being set forth from the standpoint of operation.

Operation As above mentioned, the system is left in the condition established for the last direction of traiic with the exception, of course, that the manually controlled entering signals 6 and 15 are at stop. Also, all of the signals except the entering signals 6 and 15 as well as the leaving signals 7 and 14, are normally dark. These signals adjacent the respective interlocking areas are manually controlled and are normally illuminated so as to provide the proper signal indications for local switching train movements. More specitically, the lamp L of signal 6 is energized through a circuit including back contact 16 of relay 6DP (see Fig. 3A). A similar circuit is, of course, presentrn Fig. 3E for signal 15. The controls for signals 7 and 14 have not been shown, since they vrelate more particularly to the track layouts and signalling conditions of the respective interlocking areas.

For the purposes Vof the present disclosure, lithas been assumed that traffic was last established from west to east. For reasons later explained, this `leaves the system in a condition controlling signals and 12 to yellow indicating positions and signal 8 to a green indicating position in spite of the fact that energy is` applied -to both ends of the line circuit organization. The coniiot -between the application of energy in opposite directions ordinarily occurs in the line wires for the end track sections. Although this may not be invariably true, it is sulllciently predominate as to assume this condition for the purposes of the disclosure. Also assuming the s'ig nal 14 is manually controlled to stop, the line circuit organization is energized at signal 14 with steady negative energy which controls the signal 12 to a yellow indicating position. The line circuit for signal 10 is thus energized with steady positive energy by 'thev apparatus at signal 12, so that this signal 10 also assumes ayellow indicating position and in turn controls the line circuit to signal 8 with positive and negative potential alternately .applied at intervals. This causes the signal 8 to be .controlled to a green indicating position and to endeavor to similarly energize the line circuit extending to signal 6, but due to the fact that energy is also applied to the Vline circuit at signal 6, no control is eiected.

More specically, with the traic direction relay WFR of Fig. 3E deenergized, the line Wires 19 and 20 are energized from through a circuit including back contact 21 of relay 14GYP (see Fig. 3E), back contact 22 of relay ldFLP, back contact 18 of relay WFR, front ycontact 79 of relay ISTR, line wire 20, front contact 2,3

of relay HTR, back contact 24 of relay 13FLP, hack contact 25 of relay 13S, back contact 26 of relay 13GYP, windings of relay 12DR and 12HR in series, back contact 27 of relay 13GYP, back contact 28 of relay 13S, back contact 29 of relay 13FLP, front .contact 3.0 of relay 12TR, line wire 19, front contact 103 of relay ISTR, back contact 17 of relay WFR, back contact 31 of relay 14FLP, back contact 32 of relay 14GYP, to The steady energy which flows in this circuit is in such a direction as to be characterized as a negative energization and cause the contacts of relay 12HR to be steadily picked up. This negative energization of the line circuit is steady due to the `fact that the relay `14PM is steadily deenergized while the signal 14 is at stop.

Referring to Fig. 3D, it will be seen that the steady energization of relay 12HR closes its front contact 33 to energize the relay 12HD because back contact 42 of 13HD is closed. lt might be noted that the closed condition of front contact 134 does not effect the energizetion of its associated relays at this time. The relay 12HD completes an energizing circuit for the mechanism of signal 12 from through a circuit including front contact 34 of relay 12TR, back contact 35 of relay IZDPP, mechanism of signal 12, back contact 36 of relay 12S, front contact 37 of relay 12HD, back contact 38 of relay 12DPP, to The energy which ows in this circuit is in such a direction as to cause the signal 12 to be operated to its yellow indicating position.

With the signal 12 mechanism operated, its contact 43 is operated to the right to energize the relay 12GYP through an obvious circuit. The picked up condition of this relay 12GYP connects steady positive energy to `the line circuit for the next section to the rear.

More specitically, a circuit is closed from (-'i-.) through contact 44 and 45 of signal 13 (see Fig. 3D) in a stop position, back contact 46 of relay 13FLP, back contact 47 of relay 13S, `back contact 48 of relay 13GYP, windings of relay 12A, front contact 49 of relay 12GYP, back contact 59 of relay 12S, back contact 51 of relay 12FLP, front contact 52 of track relay ISTR, line wire 53, front contact 54 of relay 10TR, back contact 55 of relay 11F-LP, "back contact '56 tof' :relay (11S, :back .contact 57 .of relay '11GYP, :windings .ofA `'relay r10HR and 10DR in series, lhack lcontact l58 of relay IIGY'P, `*back contact 59 of relay HS', backcontact 60' of relay 11FLP, front contact 61' `of relay 10TR, line wire 62, front contact 63 of relay ISTR, back contact 64 .of relayy 12FLP, 'backfcontact 65 of relay 12S, yfront contact `66 4of relay 12GYP, vto (-9. 'The steady energy which flows in this circuit -is in lsuch a direction as to characterize a positive venergization for the line relays and causes the relay 10DR to `be steadily picked iup.

It should -be noted at this point that the steady applicat-ion of positive .energy to the line wires 53 and 62 includes the approach rela-y 12A in series, -so that this approach relay 12A is picked up closi-ng its front contact 81 to energize its repeater relay 12AP. The open condition of back contact 39 ofjrelay 12AP removes energy from the lighting circuit of the lamp of Vsignal 12, and Contact 39 is not again closed until a train approaches this signal.

The steady closure of front contact 67 of relay V10DR (sec Fig. 3C) energizes relay l0iHD which completes the energizing circuit for the signal 10 vvmechanism at front contact 68. The remaining portion of the circuit willfbe understood by analogy to the circuit pointed out in detail forsignal 12. Also, the direction ofr current flow in this circuit is the same as for signal 12 and actuates the signal 10 to a yellow indicating position.

The steady picked up condition of relay '10DR closes its front contact 69 to energize the relay 10DP through va circuit also including back contact 70 of relay 10i-IR. This energized condition of relay 10DP closes its front .contact 71, but the relay IUDPP is not energized since the relay lHR is steadily deenergized and front Contact 70 is open. However, the closure ,of front contact 72 of relay 10D? Completes an energizing circuit for the flashing relay lil-FL. More Specifically, contact 73. of A.Signal 10 is, 0f course, moved t0 its .rishthaud .position with the .signal 10 Controlled t0 `its cauficn vindicating ,Position which enersizes therelay IOGYP and also supnliestenerfgy through front contact 72 o f relay 10,131?, winding ,of relay MFL, back Contact 74 of ,dashing relay MFL, to (-j) `The ashing vrelay MFL, thus energized, is intermittently interrupted by its kovyn back contact 74 so as Ato 4be ,intermittently operated in the usual fashion .Qf a =flashing relay. lts front contact 75 `is therefore intermittently .closed to directly energize its repeater ,relay V410FLP..

The picking up .of relay `IOGrYP (see Fig. 3C) applies energy to the `line circuit to the rear. vMore specifically, energy is vapplied from (+L `through a `circuit including contact in its left hand position, contact 15,1 in its right `hand position, back contact 152 of relay llfFLP, hack contact 153 of relay 11S, back `contact 154 .of relay l-iGtjP, windings of approach relay 10A, front contact 155 of relay IGGYP, 'back ,contact 15.6.01? relay 10S, hack contact 8,3 of 4relay 10FLP, front contact 157 of relay MTR, .line wire 84, front contact L16 ,of ,track relay STR (see Fig. 3B), back contact 158 of relay 9FLP, back contact 159 of relay 94S, back Contact 1,69. Vof Vrelay SGYP, windings of ,relays .SHR and [SDR .in series, back contact 161 of relay 9GYP, back .contact 1 62 of relay 9S, back Contact 163 of relay 9FLP, `front contact 117 of relay STR, `line wire .85, front contact 164 of relay HTR, back contact 82 .ofrelay lFLP, back contact 165 of relay 10S, front Contact 166 .of relay 10G'YP, to

This positive energization of the line .wires 84 and 85 is intermittently reversed to a negative ,energization by the relayv lit-FLP. For example... the energy which'ie connected to line wire 84 through front contact `lt55 is applied to line wire 85 through front contact 82 of relay ltlFLP, While the ,line WillieV 84 is connected to through front contact 83. This intermittent reversal of energization occurs at some suitable 'rate so that ypositive and negative energizations are caused vto koccuralternately. It should be noted that both the positive and the negative energization of the line wires 84 and 85 is by the supply of energy in the same direction through the approach relay 10A in series. For this reason, this relay 10A remains steadily picked up during the intermittent and alternate energization of the line circuit. However, if the travel time between the front and back points of the contacts of the relay lFLP is too long forthe relay 10A to remain picked up, its actual control is made continuous by reason of its slow acting repeater relay 10A? being directly controlled through front contact 17?. However, if desired, the relay 10A might be made slow acting rather than employing the repeater relay. With relay 10AP steadily picked up, the dashing circuit for lamp L of signal 10 is open at back contact 76, and signal 10 is dark.

Referring to Fig. 3B, it will be seen that the alternate positive and negative energizations of the line wires 84 and S5 causes the relays SDR and Sil-IR to be aitemately picked up. During the positive energizations of the line, relay SDR is picked up and relay SHR is dropped away so that relay 8D? is energized through back contact 37 and front contact 86. During negative energizations of the line relay SHR is picked up and relay DR is dropped away so that relay SDPP is energized through front contact 87, back contact 88 and front contact 89. Since these relays SDP and SDPP both have slow releasing characteristics, they remain picked up between the successive energizations which close their respective pick up circuits.

The intermittent operation of relays SDR and SHR alternately is effective to energize the relay SHD through front contacts 91 and 92, so that relay SHD remains steadily picked up. Thus, the signal 8 mechanism is energized through a circuit closed from and including front contact 93 of relay STR, front contact 94 of relay SDPP, front contact 95 of relay SHD, back contact 96 of relay 8S, signal 8 mechanism, front contact 97 of relay SDPP, to The energy which ows in this circuit is of such a direction as to cause the signal 8 mechanism to be actuated to its clear indicating position. For this reason, relay SGYP is energized from (-1-) through a circuit including contact 105 in a left hand position, contact 106 in a left hand position, windings of relay SGYP, to Energy is also fed through these contacts 105 and 106, to the dashing relay SFL through contact 104 of relay SDP.

Under these conditions, energy is applied to the line wires 110 and 111 through a circuit closed from and including signal contact 171 in a left hand position, f

signal contact 172 in a right hand position, back contact 173 of relay 9FLP, back contact 174 of relay 9S, back contact 17S of relay 9GYP, windings of approach relay 8A, front Contact 176 of relay SGYP, back Contact 120 of relay 8S, back contact 177 of relay SFLP, front contact 114 of relay 9TR, to line wire 119. The return line wire 111 is connected through front contact 115 of relay 9TR, back Contact 178 of relay 8FLP, back contact 121 of relay 8S, and front contact 179 of relay SGYP, to This application of energy is in such a direction as to characterize a positive energization of the line wires 11i) and 111, but since the flashing relay SFLP is operating, its repeater relay ZFLP intermittentlyr picks up closing its front contacts 177 4and 178 to reverse the energization to characterize a negative energization of the line wires.

As mentioned above, under normal conditions with signal 6 manually controlled to stop, energy is also applied at such signal location to the line wires 110 and 111. More specifically, a connection is made from (-l) through back contact 181) of relay 7GYP, back contact 181 of relay 7FLP, back contact 182 of relay EPR, front contact 113 of relay GTR, to line wire 111. The return connection from wire 110 is through front contact 112 of relay GTR, back contact 183 of relay EPR, back contact V8 184 of relay 7FLP, back Contact 135 of relay 7GYP, to

It can thus be seen that when the positive energy is applied to the line wire 11@ atthe signal S, its battery is in series with the battery at the signal 6 location so that an added amount of energy flows through the line circuit which energizes the relay 8A; but, when the energization of the line wires is reversed at the signal 8, the .two

batteries are in opposition and no energy flows. Thus, the lrelay 8A is intermittently pid-:ed up and dropped. However, its Iront contact 186 intermittently energizes the slow acting repeater relay SAP, which is suiciently slow acting as to remain picked up between successive energizations. This maintains back contact open and keeps the lamp of signal 8 deenergized until a train approaches, as later explained.

The signals for west bound tr-afilc do not have their respective approach relays energized, but the circuits for the respective lamps are taken through the back contacts of the HD relays for the opposing direction, which maintain these lamps deenergized. More particularly, referring to Fig. 3B it will be seen that the lamp L of signal 9 has its circuit taken through back contact 187 which is open under the conditions above described. A similar circuit is provided for each of the other signals 11 and 13. I

Let us assume that the operator at tower A desires to send an east bound train through the single track stretch. -First, he communicates with the operator at tower B via telephone, telegraph, or other communication means, and consults with the operator at tower B to determine whether or not the operator at tower B can receive east bound traflic. lf the operator at tower A finds that east bound traffic will be received by the operator at tower'B, it is agreed between 'the two operators that east bound traftic may be established. The operator at tower A then actuates the control lever for signal 6 which through suitable means not shown etlects the energization of relay 6KB. This closes front contact 158 to energize the direction relay EFR through an obvious circuit.l The signal 6 cannot be cleared immediately until it is determined Whether or not energy is being supplied to the line circuits frorn the signal 15 location. The picking up of relay EPR and the opening of back contacts 182 and 183 disconnects the source of energy at the signal 6 location and the closure ot these front contacts connects the line relays GDR and GHR to the line wires 111% and 111. Assuming that the single track stretch is unoccupied and that the operator at the east end at tower B has done nothing to disturb the west direction relay WFP., the application of alternate polaritics to the lines wires and 111 causes the relay 6HD to oe energized through front contacts 19S and 191. Also, this operation of the line relays causes the relays GDP and GDPP to be energized through circuits that will be understood by analogy to the above description. Thus, a circuit is closed Afor the signal 6 mechanism from (-l-), through a circuit including front Contact 192 of relay GRD, front contact 193 of relay 611D, front contact 194 of relayy GDPP, windings ofniechanism M of signal 6, front contact 195 of relay 6DPP, to The energy which llo-ws in this circuit is in such a direction as to actuate the spectacle SP to a green indicating position in which the green roundel G is in the light projecting path. The lamp L is steadily illuminated by reason of the closure of t'ront Contact 112 of relay dDPP. The ashing relay GFL is not in operation due to open back contact 196.

ln brief, the tumble-down line circuits have acted section by section to bc built up to the signal 6, since energy is applied at the signal 1S, and since there is no other traic in the stretch of singletrack. lf there were a west bound train in the stretch of single track, there would be no energy feeding to the relays 6DR and GHR so that signal 6 could not be cleared in spite'of action by the operator to energize relay 6RD. However, the

- picking up of the relay 6RD followedy by the picking up energization of relays 6DP and 6DPP.

of-relay EPR would remove energy from4 this' end of 'the line circuits and would place all intermediate signals 15. Since the present invention resides more particularly in the signal control circuits for four indication signals over a single track stretch having signals for both directions, such features have not been disclosed herein.

Let -us assume that the clearing of signal 6 is accepted .by an' eastbound train which proceeds into the track section 6T. This deenergizes the track relay 6TR opening frontcontacts 112 and 113' to deenergize the line circuit including line Wires 110 and 111. The relays :SDR and 6HR are therefore deenergized which results inthe de- This restores the signal 6 to stop.

The Opening of the line circuit also deenergizes the yapproach relay 8A which in turn opens front contact 186 and deenergizes its repeater relay 8A? to close 'back conta'ctl'. This completes the energizing circuitv for' the lamp L for signal 8 from through a circuit includ- 'ing back contact 10d' of relay SAP, back Contact 101 of relay BHD, front contact 102 of relay' SDPP, Lamp L,

to Thus, Ias theeast bound train proceeds into the track' section 9T it finds the signal 8 giving a green lindication sof that it can proceed at authorized speed toward the signalV It).

. As the ltrain passes the signal 8 into track section 8T, the track relay 'STR is deenergized opening iront contacts 116 and 117` to deenergize the' relays 3R and SHR. These relays in ceasing theirintermittent operation, previously described, causes the release of relays SDP and SDP? as well as relay BHD; This controls the signal 8 to stop by deenergizing the mechanism o the signal. Also, the directional stick relay 8S is picked up by reasonof a circuit closed from (-l-), andincluding back 'contact 93 of track relaySTR, front contact 11S of relay SHD, windings of relay 8S, to This pick up circuit for the relay 8S is completed as soon as the track relay STR releases and during 4the release time of the relay SHD. As soon as relay SS picks up, it vcloses front contact 1,19 to /shuntthe front contact 11S of relay SHD" sogthatv upon the closure of back contact 118 'a holding stick circuit is closed for the relay SS. The picking up ofthe directional stick relay opens its back contact 96 to assure that' the signal 8 cannot be energized. Also, the closure oi? its front contacts 120 and 121 erl'ects the connection of the sourcefa't this" location to the line wires 110 and '111 in a direction to characterize a negative energization .of the line wires. This causes the relay 6HR at signalr` 6to be steadily energized and pick up the relay 6HD, assuming that'the operator at tower A hasI kept relay 6R13 picked up for east bound trahie. Such energization. of the relay Hl)v would permit an east bound train" to proceed on a caution indication. This is because under such circumstances the relay DPl is energized. However, if such' following trains are permitted to proceed into the single track stretch, the operator at tower B sadvised so that he knows what trains to expect.

When the east' bound train enters the track section 8T 'and proceeds toward the signal 10, as above'men- 4tio'ned, the line circuits are opened deenergizing the relay 10A and approach lighting the signal 10. 'The signal 1G is controlled to a yellow indicati-ng position by the -stead-y positive energization of the line circuit including line Wires 53 and 62. This causes the relay MDR to 'be steadily picked up resulting in the steady energization of relay 10D? and the open condition or back contact 8G. Thus, the hashing relay 10FL is in operation sobaekco'ntact 78` of flashing relay NFL, lamp L, to

This flashing` yellowindication of signal lil advises the trainman` that the second signal inr advance is at stop and that he should govern his train accordingly.

Asthe train passes the signal 10, thev directional stick relay 10S is picked'up in a manner which will be' readily understood by analogy to the description for directional stick relay 8S; Such energization of the directional stick relay 10S' causes the closure of front contacts 156 and 16S to apply a steady negative energization to the line wires 84 and 85. This effects the steady energization of therelay SHR andin turn picks up the relay SHD. This `releases the directional stick relay 8S and permits the operation of the signal' 8 to a yellow indicating position, which in turn causes a steady positive energiz'ation of the lline wires`1'10 and 111. If'the operator has maintained relay 6R15 picked up for east' bound traic this would pick up? the'relay 6DP" and allow the signal 6 to give a ilashingyellow indicationv by reason of the front contact 16 causing theashing'relay 6FL to operate. Since both the contacts 16v and y112 would be open, the front contact 197 of the hashing relay 6FL could apply energy intermittently to the lamp L of signal 6;

As the east bound train proceeds and approaches signal 12, it', ofcourse, is approach lighted by reason of a circuit' closed from (4;), and including back Contact 39 of relay IIAP, vback contact 40 of relay 13T-ID, backv contact 41 of relay 12D?, lamp L of signal 12, to This steadyyellow illumination of the signal 12 advises the trainrnan` that the next signal in advance is at stop. As the train proceeds past the signal 12 at the proper speed, the directonall-stickrelay 12S is picked up. This applies al steady negative'energ'zation to the linewires 53- and 62"' which is effective at signal 10 to release the directional stick relay 10S and cause a steady positive energization to be appliedto the line wires 84 and S5 extending to signal 8.. At signalsv the line wires 110 and 111 are now supplied with opposite polarities alternately so that the signal 6l could be Operated to a clear indicating position, if desired.`

In the above description, it is assumed that the signal 141 is `standing atV stopso that the east bound train approaches prepared* tostop'. Such eastbound train will, of course, await the orders of the tower B. The operator at tower B may hold the train at signal 14 until traine conditions withinhjisare'a are proper, or he may`- irnmedia'tel'y clear the signal' 14'to allow the train to proceed k intohis interlocking area. Oh the other hand, tl'reolgner'ator at tower i'tnayV clear the signal ,14 in anticipation of scribedfwhich resultsr in theA picking up of the relay 12HD and the release of thel directional relay 12S.

In the aboveI description, it will be noted that if the east bound train proceeds past kthe signal 8, the directional stick relay 8S picks upV and applies energyy to the line wires andl 111. f manual operation or automatic means restores the relay 6RD to a deenergiz'ecl posit-ion, the directional relay EPR is released and energy is also applied to the line' wires at this location. These two energies oppose each' other or' add together as above described. But it' should be noted that the energized condition of the relay 8S prevents any response of the relays 9HR and 9DR. Upon the' continued passage of the train, energy is restored to the-line wires 84 and 85 which picks up the relay SHD. This releases the directional stick relay 8S by opening back contact 118. Also, the closure of back contact 96 of the directional stick relay permits the signal 8 mechanism to be operated to the caution position in which the relay SGYP is energized. There is a short interval of time between the closure of back contact 96 and the picking up of the relay SGYP during which the energy applied to the line Wires 110 and 111 at the location of signal 6 can feed through back contacts 120 and 121 to the relays 9HR and 9DR. The picking up of either of these relays 9HR or 9DR cannot energize the relay 9HD because of the open back contact 198 of relay SHD. ln this Way, the signal 9 is prevented from being controlled during such a transition. As soon as the signal 8 responds and relay SGYP picks up, then a positive steady energization is applied to the line wires 110 and 111 and the energy contiict takes place in such wires, as previously described. Y

In this way each directional stick relay applies energy to the line wires for the section in the rear of an occupied section and as the train progresses such energy is applied section by section and holds the condition thus established behind the train. For this reason it is apparent that the conditions for the last direction of tratiic are maintained in spite of the fact that the operator at the entrance end, or automatic means, causes the restoration of the direction control relay at that end.

In connection with the above transition period just described, it is to be understood that the response of a signal followed by the energization of its green-yellow repeater relay GYP is shorter than the release times for the HD relays and for this reason the progress of `thetrain from section to section does not interrupt the control established behind it.

Although the above description is given more particularly from the standpoint of east bound train movements, it is to be understood that west bound train movements may be made in a similar Way following an agreement between the operators at the towers A and B upon the establishment of west bound traic. The operator at tower B by manipulation of his signal control lever for signal effects the energization of the relay 15LD. This in turn closes its front contact 122 to energize the direction control relay WFR. The opening of back contacts 17 and 18 removes energy from the line wires 19 and 20 and causes the tumble-down of the circuit conditions previously established. This permits the energy applied at signal 6 to cause the circuits to build up section by section from that end and eiect the energizationrof the line relays ISHR and 1SDR in a manner analogous to that previously described for the opposite direction. This response of the line relays to the proper control in accordance with the existing conditions allows the signal 15 to clear and tratiic to proceed in the usual way.

Although it is believed that this operation of the system for the establishment of west bound trac will be readily understood by analogy, it may be helpful to point out the operation especially with respect to'v signal 9 of Fig. 3B. Assuming that the signal? is at stop, a steady ynegative energization is applied to the line Wires 110 and 111 which effects the picking up of the relay 9HR following the release of the relay SGYP as a result of the tumble-down of the circuits for east bound trahie. This energization of relay SHR closes its front contact 199 and energizes relay 9HD since contact 198 ofl relay BHD is now closed. The picking up of relay 9HD closes an energizing circuit for the mechanism of signal 9 from through a circuit including front contact 200 of relay 9TR, back Contact 201 of relay 9DPP, mechanism of signal 9, back contact 2m vof relay 9S, front contact 293 of relay 9HD, back contact 2134 of relay 9DPP, to.

( This operation of the signal 9 actuates its contact 171 to the right to energize relayt9GYP which effects the application of steady energy tothe line Wires 34 and 85. This energy is in such a directionas to charf- 12 acterize a positive energization and controls the signal 11 Yto a yellow indicating position. The signal 9`is not illuminated since its circuit is opened'by the approach relay '9AP when the line circuit conditions have stabilized. Since all of the double intermediate signal locations are organized in a similar Way,it is believed that further operations for the establishment of west bound traffic will be unnecessary. f Y

Referring to Fig. 3B it will be noted that various in'terlocks are provided to prevent apparatus for opposing directions to respond at the same time. For example, 'energy is not applied to the line Wires and 111 unless it is assured that the signal 9 is at stop as indicated by the closure of back contact 17S of relay 9GYP. A 'similar check is provided by back contact 174 of directional stick relay 9S. Likewise, the back contact 173 vof relay 9FL assures that the dashing relay 9FL and` its associated control is at stop conditions.

Itis to be understood that the usual protective features may be employed with the system of the present` invention to prevent the reversal of traiic direction inadvertently in front of an oncoming train by the use of suitable timing means which prevents the reversal of traic for a limited time after an enteringsignal has vonce been cleared and then returned, to stop.

From the above description, it is also apparent that the system of the present invention may be readily used with centralized traiiic control systems of the code type, since it requires a minimum number of controls. For example, all that is required to establish any particular direction of trahie Ais to send a signal control tok the entrance end of the single track stretch and the direction of traffic is automatically set up. This is due to' the fact that energy is normally applied to the line wires at both ends of the single track stretch and therefore is immediately available to allow the circuits to build up section by slection when the energy at the entrance end is removed. In such a system, however, it is also desirable to provide check locking which may be provided by a separate circuit organization or may be provided at the central oice on the control machine all in accordance with conventional practice.

Having thus described a block signalling system as one speciiic embodiment of the present invention, it isdesired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume; and, it is to be further understoody that 'various modilications, adapta- A tions, and alterations may be applied to the specitic form shown to meet the requirements of practice, Without in any manner departing from the spirit or scope `of the present invention.

What we claim is:

l. In a signal system for railroads, a stretch of track having signals for both directions at aplurality ofvspaced locations to divide said stretch into a pluralityof`sections, a pair of line Wires extending through each of said sections between the signal locations at the opposite ends thereof, relay means at each signal location for each pair of line wires terminating at that location, a source of energy at each signal location, circuit means at each signal location for connecting Ysaid relay means to their respective pair of line wires, other circuit means governed by such relay means at a signal location in response to the energization of one of the relay means for one pair of line wires elective to disconnectl the relay means from the other pair of line wires and instead connect said source of energy thereto, whereby the application y of energy to the pair of line wires extending to either end of said stretch effects the energization of each successive pair ofline wiresrin turn to energize the corresponding relay means at each said signal locations, said other circuit means at each signalr location being effective forselectively steadily energizing its pair ofuline Wires with one polarity or the other or intermittently; energizing .its pair Vof .line wires with both polarities yalternately depending upon the -character of energization of the linel wires for the lpreceding -track section, and signal control vcircuit means at each signal location for controlling the `signal for one direction or the other depending upon which of the relay means at that location is energizedv to ,give a distinctive signal indication for each `different conditionof its .line circuit energization for the section over which such signa-l governs traic.

2. In a signal system for railroads having a stretch of track with signals at spaced locations for governing tralc in both directions, respective pairs of line wires connecting successive signal locations, relay means associated with the respective pairs of line wires terminating vat each signal location, a source of energy at each signal location, circuit means at each signal location governed 'in accordance With the energization of said relay means :associated with either pair of line wires terminating at that llocation for disconnecting said relay means -associated with the other pair 'of line wires terminating at that location-'and connecting said source thereto, `whereby the `alsgplication of venergy to the pair of line wires Yextending* to either end of said stretch etfects the energization of the corresponding relay means at each of said signal locations for governing tralllc toward that end of said stretch having energy applied to the line wires, other circuit means at each signal location for selecting the character of energization of the pair of line wires in accordance with the character of energization of the preceding pair, said other means being capable of steadily energizing the then connected pair with one polarity or the other or intermittently energizing such pair with both polarities alternately at a predetermined rate, and signal control circuit means controlled by said relay means at a signal location for governing the indications of said signals to give four different indications in accordance with the selective energization of the associated pair of line wires.

3. In a signal system for railroads, a stretch of track having signals for both directions at spaced signal locations along the stretch to divide said stretch into a plurality of sections, a pair of line wires extending through each section, relay means at each signal location associated with each pair of line wires terminating at that location, a source of energy at each signal location, circuit means at each signal location governed by the energization of one relay means for causing the disconnection of the other relay means at that location from its pair of line wires and connecting said source of energy thereto, other circuit means at each signal location governed by said other relay means at that location upon its energization to disconnect said one relay means from its pair of line wires and connect .said source of energy thereto, whereby the application of energy to the line wires at one end of said stretch elects the energization of said line wires for the successive sections for energizing the corresponding relay means at each of the several signal locations, and whereby the application of energy to the line wires at the opposite end of the stretch effects the energization of the pair of line wires for successive sections to energize the corresponding relay means at the signal locations for the opposite direction, an intermittently operable relay means at each signal location, a signal control circuit means at each location for controlling the indications of said signals at that location for one direction or the other depending upon which of the two relay means at that location is energized, said signal control circuit means acting in response to a particular condition of energization of said relay means for causing said intermittently operable relay means to etfect the dashing of the corresponding signal and at the same time to cause said line circuit for the adjacent section to be energized with opposite polarities alternately.

4. In a signalling system for railroads, apparatus at a signal location having two control line wires extending thereto, polarized relay means connected in said line wires and distinctively responsive to the polarity of energizasesgado tion ofsaidlinewir'cs, a .thrposition light signal mechanismy normally .biased to ay particular position indicating stop,a dashing re'lay.4 circultmeausfcontrolled by said polarizedrelay means wlten steadily-energized with either polarity tocause said signal"mecliansmto be operated to a di'ferentposition indicating cautionA and' when. intermittently energized with opposite polarities' alternately tof cause .said signal mechanism tobe operated to a third `positioninc'licating.l clear;..a control circuit means effec- 'tiveto cause operation of said :dashingr relay when .said ,polarized relay :meansis-steadily energized with a particular polarity, and circuit meanscontrolled by said a'shingrelayfor'cansihgsaid'lliglttsignal to llash when it is in saidposition indicating. .caution while said line circuit is steadily energized'with saidfgparticular 'polari-ty.

5.r In a `signalling system forralroads, a 'linecircuit h avingsteady ,positive'energ steady negative energy or intermittent positive and'negative energy alternately, applied' thereto accordance witlr'trafic conditions, relay means connected to" saidiline-f'circuit and distinctively controlled vto either `olii-three' different conditi-ons in accord- 'ance the characteristic e'nergiza'titantotl said line eircuit, a light signal mechanism controlled by said relay means to operate to one position when said line circuit is steadily energized and to operate to a different position when said line circuit is intermittently energized, a ilashing relay controlled by said relay means to operate when said line circuit is steadily energized with one polarity, a lamp in said signal mechanism, and circuit means governed by said relay means and said flashing relay for intermittently energizing said lamp when said line circuit is steadily energized with said one polarity and for steadily energizing said lamp when said line circuit is steadily energized with the opposite polarity or is intermittently energized with opposite polarities alternately.

6. In a signalling system for railroads, a signal mechanism operable to different indicating positions including clear, caution, and danger, a flashing relay operated while said signal indicates clear and caution, a lamp in said signal, circuit means for at times causing said lamp to be intermittently energized by said flashing relay, a line circuit extending to the rear of said signal and having steady positive or negative energy applied thereto in accordance with the then existing indication of said signal, and circuit means governed by said tlashing relay to intermittently reverse the connections of said line circuit when said signal indicates caution with its said lamp flashing and also when said signal indicates clear.

7. In combination, a section of railway track, a signal for governing traflic of said section, a pair of conductors extending through .said section and having steady energy of one polarity or the other applied thereto at the exit end of such section in accordance with tratllc conditions and having both polarities applied alternately at recurring intervals in response to a third trailic condition, two polarized relays connected in series to said pair of conductors at said signal location, said relays being respectively responsive to opposite polarities, a slow acting relay energized when either of said polarized relays is picked up and elective to be maintained picked up when said polarized relays are alternately picked up at recurring intervals, a repeating relay energized when one of said polarized relays is energized, another repeating relay energized when the other polarized relay is picked up and said llrst repeating relay is picked up, and signal control circuits for actuating a three indication signal to indicate stop when said slow acting relay is deenergized and to indicate one proceed indication when said slow acting relay is energized and said repeater relays are deenergized, to indicate another proceed indication when said slow acting relay and both of said repeater relays are energized, said circuit means including a flashing relay set into operation by the energization of said first repeating relay and being etective to cause the flashing of said signal in its trst proceed indicating position.

8. In a railway signal system, a stretch of track havsection governed by their associated vsignal circuit means governed by said signal control relays for causing its signal to indicate stop when both of said signal ycontrol relays are steadily deenergized, to actuate said signal to a rst proceed indication position when one of said signal control relays is steadily energized, to actuate said signal to a second proceed indication when the other of said signal control relay is steadily energized and `to actuate said signal to a'second indicating position when said two signal control relays are energized alternately, a asher relay at each signal location, circuit means for setting said asher relay'into operation whenever said other signal control relay is energized with said other polarity, said circuit means for controlling said signals causing said signal to flash said first proceed'indication when said ashing relay is set intofoperation by said other polarity, and circuit means at each signallocation for causing energy of one polarity to be applied to the pair "of line wires extending to the rear of that signal location when that signal indicates stop, and causing the other polarity to be applied to said line wires when said signal is giving said rst proceed indication, and causing said opposite polarities to be alternately applied at intervals to said such line wires when that signal is giving the rst proceed indication but is being flashed, said means also acting to similarly apply said opposite polarities alternately when the signal at that location is giving said third proceed indication.

References Cited in the tile of this patent UNITED STATES PATENTS 1,660,332 Hewett Feb. 28, 1928 2,076,317 Allen Apr. 6, 1937 2,122,373 Hormats June 28, 1938 2,168,816 Young Aug. 8, 1939 2,291,579 Judge July 28, 1942 2,326,991 Young Aug. 17, 1943 2,355,499 Allen Aug. 8, 1944 2,638,536 Tizzard ---a May 12, 1953 

